The Angiosperm Phylogeny Group, or APG, refers to two international groups of systematic botanists who came together to try to establish a consensus view of the taxonomy of flowering plants that would reflect new knowledge in angiosperm relationships molecular systematics. Botany, plant science(s, phytology, or plant biology is a branch of Biology and is the scientific study of plant Life Taxonomy is the practice and science of classification The word comes from the Greek, taxis (meaning 'order' 'arrangement' and, nomos The flowering plants or angiosperms ( Angiospermae or Magnoliophyta) are the most widespread group The flowering plants or angiosperms ( Angiospermae or Magnoliophyta) are the most widespread group Two papers resulted from these collaborations, commonly referenced as 'APG I (1998)' and 'APG II (2003),' and were largely attempts to deal with the deficiencies in prior angiosperm classifications (Cronquist 1981, Thorne 1992 and 2001, Takhtajan 1997) as seen by phylogenetic theories based on analysis of DNA. Armen Leonovich Takhtajan or Takhtajian (Армен Леонович Тахтаджян surname also transliterated Takhtadjan or Takhtadzhian (born June 10, Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known
The first paper by the APG marked an important change in how angiosperm classifications were done, as prior classification systems had been done by one or two scientists, while this paper was the effort of 29 botanical systematists to make sense of the large number of molecular phylogenies being studied in the angiosperms. This made angiosperms the first large group of organisms to be systematically reclassified largely on the basis of molecular characteristics. 
The flowering plants (also known as angiosperms, Angiospermae, Anthophyta, Magnoliophyta), are one of the groups of organisms whose classification has been affected most radically as molecular data became available. The influential classification scheme published by American botanist Arthur Cronquist in 1981, the Cronquist system, had been increasingly challenged during the 1990s. Arthur John Cronquist (1919&ndash1992 was a North American botanist and a specialist on Compositae. A system of plant taxonomy, the Cronquist system is a scheme for the classification of flowering plants (or Angiosperms) The molecular data that have become available since around 1990, analysed by cladistic methods, have clarified our views of some relationships and radically changed others. Cladistics is the hierarchical classification of Species based on evolutionary ancestry This has made possible a much closer approach to the phylogenetic goal of making classification reflect descent.
The rapid increase in knowledge has led to many proposed changes in classifications, and these pose problems for all users of classifications (including encyclopaedists). By bringing together researchers from major institutions world-wide, and publishing jointly, the Angiosperm Phylogeny Group have sought to provide a stable point of reference, publishing the APG-system (1998). This system deals mostly with higher ranks and, as there are still severe limits to our knowledge, a firm classification is not possible in all cases.
The system is based on two chloroplast genes and one gene coding for ribosomes. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. Ribosomes ( from ribo nucleic acid and "Greek soma ( meaning body") are complexes of RNA and Protein that This selection of genes from cell organelles is significant; zoological taxonomy similarly uses genes of mitochondria. In Cell biology, an organelle (pronunciation /ɔː(rgəˡnɛl/ is a specialized subunit within a cell that has a specific function and is usually separately enclosed In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. The genome of cell organelles is separated somewhat from the nuclear genome, both chloroplasts and mitochondria having their own DNA, actually prokaryote DNA. The sequence of nucleotides is subject to a different rate of change compared to nuclear DNA.
The first APG classification was published in 1998 and was superseded in 2003 by a revised version (APG, 2003), known as APG II 2003 or just APG II. Its major innovations were:
Bracketed taxa are introduced to help cope with the transition from the older, morphologically based classifications to the newer, molecularly-based systems, since the process has tended to produce a number of rather small taxa, e. g. monogeneric families, which are inconvenient for users. As the APG authors note (p. 402), "We generally accept the opinion of specialists. . . but we also recognise that specialists nearly always favour splitting of groups. . . ".
Independent researchers, including members of the APG, continue to publish their own views on areas of angiosperm taxonomy, and in any case no classification is ever final; it presents a view at a particular point in time, based on a particular state of research. New results are always appearing. Nonetheless the APG publications are increasingly regarded as an authoritative point of reference.
APG II 2003 was "compiled by Birgitta Bremer, Kåre Bremer, Mark W. Chase, James L. Reveal, Douglas E. Soltis, Pamela S. Soltis and Peter F. Stevens, who were equally responsible and listed here in alphabetical order only, with contributions from Arne A. Anderberg, Michael F. Fay, Peter Goldblatt, Walter S. Judd, Mari Källersjö, Jesper Kårehed, Kathleen A. Kron, Johannes Lundberg, Daniel L. Nickrent, Richard G. Olmstead, Bengt Oxelman, J. Chris Pires, James E. Rodman, Paula J. Rudall, Vincent Savolainen, Kenneth J. Sytsma, Michelle van der Bank, Kenneth Wurdack, Jenny Q. -Y. Xiang and Sue Zmarzty (in alphabetical order). "
Institutions represented among the principal authors of the APG II classification include:
Contributions also came from many other institutions world-wide. The Royal Swedish Academy of Sciences or Kungliga Vetenskapsakademien is one of the Royal Academies of Sweden. Uppsala University ( Swedish Uppsala universitet) is a world-class research University in Uppsala, Sweden. The Royal Botanic Gardens Kew, usually referred to simply as Kew Gardens, are extensive Gardens and botanical glasshouses between Richmond and The University of Maryland College Park (often referred to as The University of Maryland UMD, UMCP or simply Maryland) is a public research The University of Florida ( Florida or UF) is a public land-grant, sea-grant, space-grant major Research The Missouri Botanical Garden is a Botanical garden located in St